Adsorbents used in the petroleum and gas industry typically consist of alumina, silica, zeolite, or activated carbon. They are generally used for dehydration of and/or the separation of impurities and molecular components within a hydrocarbon or gas stream.
Catalysts employed in the industry generally consist of a carrier, which can be the same type of material that is used for the adsorbent plus catalytic metals. The metal is impregnated or compounded in the carrier and include noble and non-noble metals such as platinum, rhenium, cobalt, molybdenum, nickel, tungsten and palladium as well as rare earth metals. The catalysts are employed in various hydroprocessing units. For instance, when combined with hydrogen and heat such catalysts can be used to change the molecular structure of oil, as in hydrocracking. In addition, such catalysts can be employed to remove impurities as in hydrodesulfurization and hydronitrification; saturate, with hydrogen, hydrocarbon streams, as in hydrogenation; and dehydrogenate feed streams, as in reforming.
Such adsorbents, as well as catalysts, become deactivated by the build-up of coke or polymer deposits on and within the infrastructure of the particles. Such build-up continues during operation of the processing unit, seriously impairing the efficiency as well as the selectivity of the process. Such deposits are normally removed from the catalytic particles by contacting them with oxygen. The reaction, being highly exothermic, can be represented by the following: EQU C+O.sub.2 .fwdarw.CO.sub.2 +94,500 Calories
The thermal stability of the catalysts and adsorbents treated by such processes vary. Normally, the particles are destroyed at temperatures of approximately 1000.degree. F. In addition, agglomeration of the metal can occur at temperatures as low as 900.degree. F. Unless the amount of heat generated from the reaction is controlled or removed, the catalyst or adsorbent can be permanently destroyed.
A common method of controlling this exothermic reaction is to dilute the oxygen content of the gas with steam or an inert gas. By decreasing the concentration of oxygen in the incoming gas, the efficiency of the regeneration process however is decreased.
A method of efficiently removing the exothermic heat of reaction is thus desired for the processing of greater quantities of spent catalyst and adsorbents.